If you believe that NetworkManager should be allowed read access on the sysctl.conf file by default.
Then you should report this as a bug.
You can generate a local policy module to allow this access.
Do
allow this access for now by executing:
# grep NetworkManager /var/log/audit/audit.log | audit2allow -M mypol
# semodule -i mypol.pp

I haven't made any policy changes, this seems to happen when I "resume" my wireless connection, I can reproduce it by suspending the laptop, and then resuming, I'm guessing nm tries to read the state of wlan0 to make sure it's working and selinux doesn't like it.